The present invention relates to a base transceiver station in a radio communication system; and, more particularly, to a base transceiver station having a multi-beam controllable antenna system in a radio communication system, which varies a horizontal/vertical angle and a tilting angle according to variation in an amount of traffic within a sector.
From now on, a radio communication should support not only a voice service but also a high speed multimedia service including a data communication, a video transmission service, etc. However, radio resources necessary for the radio communication are limited. Therefore, various methods for effectively reusing the radio resources are being developed.
In general, a radio communication system includes a mobile switching center (MSC), a base station controller (BSC), a plurality of base transceiver stations (BTS) and a plurality of mobile stations (MS).
The MSC controls a plurality of the BSCs each controlling a plurality of the BTSs.
A signal radiated from the MS located in a service coverage of the BTS is transmitted to the MSC through the BTS and the BSC. On the contrary, a signal from the MSC is transmitted to the MS through the BSC and the BTS. Here, the BTS communicates with the MS through the radio resource and does with the BSC through the wired resource.
The BSC performs a connection between the BTS and the MSC and a signal processing for a communication between the BTS and the MSC.
The MSC performs a call processing of a subscriber, a call setup/release and functions for providing value added services.
FIG. 1 shows a conventional base transceiver station.
Referring to FIG. 1, the conventional base transceiver station includes fixed combiners 101-1 to 101-3, fixed dividers 103-1 to 103-3, amplifiers 105-11 to 105-34, combiners 107-1 to 107-3 and duplexers 109-1 to 109-3.
A service area of the BTS is divided into multiple sectors, and frequency assignments assigned to the BTS are re-assigned to the multiple sectors. The frequency assignment assigned to each sector is fixed in order to be used only for the sector.
In general, a beam pattern of an antenna is set to be wider than the service area as shown in FIG. 2A.
Referring to FIG. 2B, the FAs in each of the sectors are overlapped with each other, efficiency of frequency is considerably decreased in the overlapped region (denoted by oblique lines).
Since the mobile station always moves, distribution of subscribers in the service areas, i.e., a cell or a sector, always varies. However, a horizontal half-power beam width and a tilting angle of an antenna system located in the BTS are fixed and cannot be varied.
Therefore, though traffics in a certain sector is temporarily increased, the frequency assignments cannot be changed, thereby decreasing efficiency in use of the frequency resources.
In general, the antenna is located on a high location, which is remote from the BTS, and the antenna is coupled to the BTS by using a radio frequency (RF) cable. There is a transmission loss in the long RF cable. As the RF cable is longer, the transmission loss becomes larger.
There are a conventional mechanical down-tilting antenna system and a conventional electrical down-tilting antenna system. The mechanical down-tilting antenna system being capable of mechanically down-tilting a beam radiated from an antenna incorporated into the antenna system. The antenna is mounted atop a mast at a height above ground, e.g., in many cases about 200 feet.
In case when the orientation of a radiation beam is steered downward, the antenna must be mechanically down tilted. One of the major shortcomings is that this approach is generally regarded as too rigid and too expensive. There is an approach that electrically down-tilting the radiation beam is performed by steering the relative phases of the radiation associated with each of several radiators of an antenna.
The conventional electrical down-tilting antenna being capable of electrically down-tilting a beam 406 radiated from an antenna array incorporated into the antenna system. In the antenna system, the antenna array incorporates therein an array of radiators and a single point signal feed network provided with a scan network to couple the single point signal feed network to the antenna array of radiators. The scan network includes a plurality of transmission lines between the feed network and each radiator. Among these electrical down tilting method is a capacitive coupling method, in which an adjustable capacitance is placed in series with the transmission lines to provide a plurality of signals to each radiator of the antenna array, thus causing the desired phase shifts. A phase shifter is associated with each radiator of the antenna array such that the phase shifted beam from each radiator constructively interferes with the beam from every other radiator to produce a composite beam radiating at an angle from a line normal to the surface of the antenna. By changing the phase shift provided by each phase shifter, the beam can be scanned across the antenna surface. Another such approach is to use different lengths of transmission lines for feeding the different elements to produce a permanent electrical down tilting.
There are a number of problems associated with the above-described antenna systems. First of all, both of the antenna systems cannot steer a radiation beam in horizontal direction.
Another problem of the conventional antenna system is that it requires a number of phase shifters corresponding to the number of the transmission lines in the conventional antenna systems.
In addition, in the conventional antenna systems, it requires a mechanically complex, for example using a rack and pinion assembly or a number of phase shifters corresponding to the number of radiators, for providing the desired phase shift.
Further, the conventional antenna systems cannot steer a beam width in horizontal and in vertical,
Finally, because a beam is scanned in vertical and in horizontal by utilizing the conventional antenna systems, it has too much scan loss.
Therefore, in order to keep an output power of a signal radiated from the antenna constant, an output power of a multi channel power amplifier (MCPA) in the BTS should be increased.
Since the MCPA is an expensive device, a high capacity MCPA makes the cost for the BTS increased.
It is, therefore, an object of the present invention to provide an antenna system capable of controlling multi beams of frequency assignments by independently varying a half-power beam width and a tilting angle in vertical and horizontal direction.
It is another object of the present invention to provide a method and a base transceiver station for controlling multi beams of frequency assignments by independently varying a half-power beam width and a tilting angle in vertical and horizontal direction.
It is another object of the present invention to provide an antenna system for electrically steering a beam emitted therefrom in horizontal by using a multi-line phase shifter.
It is another object of the present invention to provide an antenna system for selectively switching a beam width in horizontal by using a switchable divider.
It is another object of the present invention to provide an antenna system for minimizing interference and maximizing cell capacity.
It is another object of the present invention to provide an antenna system for providing an optimal cell planning and meeting the real world of diverse environments.
It is another object of the present invention to provide an antenna system capable of harmonizing with communication environment.
It is another object of the present invention to provide an antenna system with a stable installation.
In accordance with an aspect of the present invention, there is provided an antenna system for controlling multi beams of a transmission signal, comprising; at least one first dividing unit for dividing an input signal into a plurality of first divided signals; at least one first phase shifting unit for shifting the first divided signals and generating first phase-shifted signals, at least one first combining unit for combining the phase-shifted signals and generating a first combined signal; at least one second dividing unit for dividing the first combined signal into second divided signals; at least one second phase shifting unit for shifting the second divided signals and generating second phase-shifted signals; and a controlling unit for generating a control signal which controls horizontal and vertical half-power beam widths and tilting angles of the input signal independently by controlling the first and the second dividing unit and the first and the second phase shifting unit.
In accordance with another aspect of the present invention, there is provided an antenna system for receiving a signal, comprising: at least one dividing unit for dividing a signal received by the antenna array into a plurality of divided signals; at least one phase shifting unit for controlling phases of the divided signals and generating phase-shifted signals; a combining unit for combining the phase-shifted signals, generating a combined signal and outputting the combined signal; and a controlling unit for generating a control signal which controls the phase shifting unit and the combining unit.
In accordance with further another aspect of the present invention, there is provided a base transceiver station for controlling multi beams of a transmission signal, comprising: at least one first dividing unit for dividing an input signal into a plurality of first divided signals; at least one first phase shifting unit for shifting the first divided signals and generating first phase-shifted signals; at least one first combining unit for combining the phase-shifted signals and generating a first combined signal; at least one second dividing unit for dividing the first combined signal into second divided signals; at least one second phase shifting unit for shifting the second divided signals and generating second phase-shifted signals; and a controlling unit for generating a control signal which controls horizontal and vertical half-power beam widths and tilting angles of the input signal independently by controlling the first and the second dividing unit and the first and the second phase shifting unit.
In accordance with further another aspect of the present invention, there is provided a base transceiver station for receiving a signal, comprising: at least one dividing unit for dividing a signal received by the antenna array into a plurality of divided signals; at least one phase shifting unit for controlling phases of the divided signals and generating phase-shifted signals; a combining unit for combining the phase-shifted signals, generating a combined signal and outputting the combined signal; and a controlling unit for generating a control signal which controls the phase shifting unit and the combining unit.
In accordance with further another aspect of the present invention, there is provided a method for controlling multi beams of a transmission signal in an antenna system, comprising the steps of: a) at first dividing unit, dividing an input signal into a plurality of first divided signals; b) at first phase shifting unit, shifting the first divided signals and generating first phase-shifted signals; c) at first combining unit, combining the phase-shifted signals and generating a first combined signal; d) at second dividing unit, dividing the first combined signal into a plurality of second divided signals; e) at second phase shifting unit, shifting the second divided signals and generating second phase-shifted signals; and f) generating a control signal which controls horizontal and vertical half-power beam widths and tilting angles of the input signal independently by controlling the first and the second dividing unit and the first and the second phase shifting unit.
In accordance with further another aspect of the present invention, there is provided a method for controlling multi beams of a received signal in an antenna system, comprising the steps of: a) at dividing unit, dividing a signal received by the antenna array into a plurality of divided signals; b) at phase shifting unit, controlling phases of the divided signals and generating phase-shifted signals; c) at combining unit, combining the phase-shifted signals, generating a combined signal and outputting the combined signal; and d) generating a control signal which controls the phase shifting unit and the combining unit.
In accordance with further another aspect of the present invention, there is provided a method for controlling multi beams of a transmission signal in a base transceiver station, comprising the steps of: a) at first dividing unit, dividing an input signal into a plurality of first divided signals; b) at first phase shifting unit, shifting the first divided signals and generating first phase-shifted signals; c) at first combining unit, combining the phase-shifted signals and generating a first combined signal; d) at second dividing unit, dividing the first combined signal into a plurality of second divided signals; e) at second phase shifting unit, shifting the second divided signals and generating second phase-shifted signals; and f) generating a control signal which controls horizontal and vertical half-power beam widths and tilting angles of the input signal independently by controlling the first and the second dividing unit and the first and the second phase shifting unit.
In accordance with further another aspect of the present invention, there is provided a method for controlling multi beams of a received signal in a base transceiver station, comprising the steps of: a) at dividing unit, dividing a signal received by the antenna array into a plurality of divided signals; b) at phase shifting unit, controlling phases of the divided signals and generating phase-shifted signals; c) at combining unit, combining the phase-shifted signals, generating a combined signal and outputting the combined signal; and d) generating a control signal which controls the phase shifting unit and the combining unit.